1. Field of the Invention
This invention relates to an anti-collision system for vehicles, for preventing a collision of the vehicle with an object such as a preceding vehicle by detecting objects in the vicinity of the source vehicle.
2. Prior Art
Recently, a so-called anti-collision system for vehicles has been proposed, which detects an object present in the vicinity of the vehicle, and issues a warning of a potential collision to the driver and/or automatically controls the vehicle to decelerate when the vehicle approaches a position where a collision of the vehicle with the object can occur.
Specifically, an anti-collision system of this kind is known, for example, from Japanese Provisional Patent Publication (Kokai) No. 61-84578, which is mounted in an automotive vehicle and constructed such that when an object is detected in the vicinity of the source vehicle by a sensor thereof, an estimated path of travel of the object is calculated in response to the present traveling speed and steering-turning angle (rudder angle) of the source vehicle, and whether there is a danger of a collision of the source with the object, which will surely occur when the source vehicle continues to travel with the present vehicle speed, is determined based on the thus calculated estimated path of travel, to thereby issue an appropriate warning to the driver and/or control the operation of the vehicle, based on the determination result.
Further, an adaptive cruise system is known from U.S. Pat. No. 5,014,200, which calculates a desired trailing distance to a target vehicle, based on the speed of the source vehicle, the distance between the source vehicle and the target vehicle, and the operator reaction time, to thereby control the speed of the vehicle to maintain the distance to the target vehicle at the desired trailing distance.
Still further, an FM radar system is known from U.S. Pat. No. 4,308,536, which irradiates a target object with over-lapped pulsed radiant beams, periodically determines from reflected signals from the beams the relative velocity and distance between the source vehicle and the object, and determines from the relative velocity and distance whether the vehicle and the object are on a collision course to provide a warning signal to the driver.
In the first-mentioned conventional anti-collision system, the speed and steering-turning angle of the source vehicle are used as parameters to calculate an estimated path of travel of the vehicle. However, the path of travel estimated based on the detected steering-turning angle does not always correspond to the actual path of travel, due to various factors, such as the road surface condition, peculiarities of the wheel tires used, wind, and other disturbances applied on the vehicle body. Further, according to the conventional system, the path of travel is calculated in terms of a line of travel, whereas the vehicle has a substantial width, which makes it difficult to determine the possibility of collision of the vehicle with an object, from the estimated path of travel in terms of a line of travel. Therefore, to carry out accurate determination of a potential collision of the source vehicle with an object, it is required to estimate the path of travel of the source vehicle in terms of an area of travel.
This requirement is not contemplated by the other above-mentioned conventional systems, either.